Here is the full list of all 57 Star Wars Knights of the Old Republic II: The Sith Lords achievements.
Complete the game on the Dark Side
Have 30 points in Treat Injury.
Have your character replace any of the Sith Lords on the main menu screen.
Acquire all Dark Side Powers.
Side with Vaklu on Onderon
Recruit Hanharr
Beat the champ on Nar Shadaa
Convince the "champ" to lose the game without playing.
Recruit the Handmaiden
Complete the game on the Light Side
Defeat Sion
Have Persuasion over 30
Have 30 points in Demolitions.
Defeat Nihilus
Kill all the Jedi masters
Side with the Queen on Onderon
Fill the Party Selection screen
Repair the damaged droid on the Ebon Hawk
Complete the Mandalorian Battle Circle
Flee Korriban after fighting Sion
Get this by starting the "Trapped" Quest on Korriban.
Loot a body on Korriban
Convince Vogga the Hutt to sell fuel to Telos.
Recruit Mira
Have 30 points in Repair.
Reach maximum Light Side points
Gain a Prestige class
Contruct your first Lightsaber
Side with the Settlers at Khoonda
Collect 10,000 credits
Recruit the Disciple
Have 30 points in Computer Use.
Get the named Lightsaber crystal
Destroy Peragus Astroids
Kill all Sith troopers before they can board the Ebon Hawk
Get your first Dark Side points
Let the Sith destroy the Peragus Asteroids
Dance for Vogga
Get your first Light Side points
Complete the Prologue
Install HK-47's unique module
Complete the Handmaiden Battle Circle
Learn Moving Meditation
Learn Force Sight
Break Hanharr's spirit
Change your mind about siding with the Settlers at Khoonda
Reach maximum Dark Side points
Win a Pazaak game with a full board
Reduce a companion's Influence to zero.
Acquire all Light Side Powers
Reach Player Level 30
Have 30 points in Stealth
Claim Darth Nihilus' mask.
Teach the Handmaiden the ways of the Force.
Deduce G0-T0's identity
Learn how to kill Jedi from HK-47
Listen to HK-47's definition of love.